Biochemistry Modules 1–3 Practice Questions 2026 |WGU
1. Which property of water is primarily responsible for its ability to act as a
universal solvent for polar molecules?
A. Ability to form hydrogen bonds
B. High specific heat
C. Non-polar covalent bonding
D. High surface tension
Answer: A
Rationale: Water’s ability to form hydrogen bonds allows it to surround and dissolve polar
and ionic substances by creating hydration shells.
2. A buffer solution is most effective when the pH of the solution is close to:
A. The pKa of the weak acid
B. pH 7.0
C. The boiling point of water
D. The concentration of the conjugate base
Answer: A
Rationale: A buffer is most resistant to pH changes when the pH is within one unit of its
pKa, where the concentrations of the acid and conjugate base are nearly equal.
,3. Which type of bond links amino acids together to form the primary structure
of a protein?
A. Hydrogen bond
B. Ionic bond
C. Disulfide bond
D. Peptide bond
Answer: D
Rationale: The primary structure is the linear sequence of amino acids held together by
covalent peptide bonds.
4. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Rationale: Secondary structure refers to local folding patterns like alpha-helices and beta-
sheets, stabilized by hydrogen bonding between the backbone atoms.
5. An enzyme increases the rate of a chemical reaction by:
A. Increasing the activation energy
B. Lowering the activation energy
C. Changing the equilibrium constant
D. Increasing the temperature of the reaction
Answer: B
Rationale: Enzymes act as catalysts by providing an alternative pathway with a lower
activation energy for the reaction.
, 6. In DNA, which nitrogenous base always pairs with Cytosine?
A. Adenine
B. Thymine
C. Guanine
D. Uracil
Answer: C
Rationale: According to Chargaff’s rules and Watson-Crick base pairing, Guanine pairs
with Cytosine via three hydrogen bonds.
7. What is the primary difference between DNA and RNA sugars?
A. RNA contains glucose
B. DNA contains ribose, RNA contains deoxyribose
C. DNA contains deoxyribose, RNA contains ribose
D. RNA contains deoxyribose, DNA contains ribose
Answer: C
Rationale: DNA stands for Deoxyribonucleic Acid (contains deoxyribose), while RNA
stands for Ribonucleic Acid (contains ribose).
8. Which amino acid is classified as non-polar?
A. Lysine
B. Valine
C. Glutamate
D. Serine
Answer: B
Rationale: Valine has a branched hydrocarbon side chain, making it hydrophobic and non-
polar.
1. Which property of water is primarily responsible for its ability to act as a
universal solvent for polar molecules?
A. Ability to form hydrogen bonds
B. High specific heat
C. Non-polar covalent bonding
D. High surface tension
Answer: A
Rationale: Water’s ability to form hydrogen bonds allows it to surround and dissolve polar
and ionic substances by creating hydration shells.
2. A buffer solution is most effective when the pH of the solution is close to:
A. The pKa of the weak acid
B. pH 7.0
C. The boiling point of water
D. The concentration of the conjugate base
Answer: A
Rationale: A buffer is most resistant to pH changes when the pH is within one unit of its
pKa, where the concentrations of the acid and conjugate base are nearly equal.
,3. Which type of bond links amino acids together to form the primary structure
of a protein?
A. Hydrogen bond
B. Ionic bond
C. Disulfide bond
D. Peptide bond
Answer: D
Rationale: The primary structure is the linear sequence of amino acids held together by
covalent peptide bonds.
4. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Rationale: Secondary structure refers to local folding patterns like alpha-helices and beta-
sheets, stabilized by hydrogen bonding between the backbone atoms.
5. An enzyme increases the rate of a chemical reaction by:
A. Increasing the activation energy
B. Lowering the activation energy
C. Changing the equilibrium constant
D. Increasing the temperature of the reaction
Answer: B
Rationale: Enzymes act as catalysts by providing an alternative pathway with a lower
activation energy for the reaction.
, 6. In DNA, which nitrogenous base always pairs with Cytosine?
A. Adenine
B. Thymine
C. Guanine
D. Uracil
Answer: C
Rationale: According to Chargaff’s rules and Watson-Crick base pairing, Guanine pairs
with Cytosine via three hydrogen bonds.
7. What is the primary difference between DNA and RNA sugars?
A. RNA contains glucose
B. DNA contains ribose, RNA contains deoxyribose
C. DNA contains deoxyribose, RNA contains ribose
D. RNA contains deoxyribose, DNA contains ribose
Answer: C
Rationale: DNA stands for Deoxyribonucleic Acid (contains deoxyribose), while RNA
stands for Ribonucleic Acid (contains ribose).
8. Which amino acid is classified as non-polar?
A. Lysine
B. Valine
C. Glutamate
D. Serine
Answer: B
Rationale: Valine has a branched hydrocarbon side chain, making it hydrophobic and non-
polar.
